During the 2019 growing season, Dr. Eric Hunt of Atmospheric and Environmental Research, Inc. will be providing weekly updates of the soil moisture index (SMI) from the Noah-MP land surface model in the NASA LIS framework for the eastern 3/4 of the U.S. where row-crop agriculture is more common. The Evaporative Stress Index (ESI) will also be included in our analysis once data for all of the U.S. are available later this month. The analysis is intended to provide the larger agricultural and meteorological communities insight as to areas where soil moisture is excessive or deficient compared to average for that location and what that may mean for impacts. It is my goal that these maps can be an early warning signal for flash drought development or where flash flooding could be likely in the coming week if heavy precipitation materializes. Please be advised that the SMI should be viewed as complementary, not a substitute, to the U.S. Drought Monitor (USDM) and that declarations of drought for a particular location should never be based on the SMI alone.
This blog post was partially supported by NASA grant NNH16CT05C.
Figure 1. The Soil Moisture Index (SMI) for the 7-day period ending 6 April 2019. Results are based on output from the 0-1 m (surface to 3.23 feet) layers in the Noah-Multiparameterization (Noah-MP) land surface model. Noah-MP is run in the NASA Land Information System (LIS) framework with the North American Land Data Assimilation Version 2 (NLDAS-2) forcing dataset. The SMI calculation is based on the soil moisture index created in Hunt et al. (2009) such that ‘5’(dark green) is the wettest and ‘-5’ (dark red) the driest for the period of record. The period of record used to calculate the SMI for the current map is 1979-present.
As of last Saturday, the SMI indicates that much of the Corn Belt is very moist for this time of year, with only a few pockets experiencing slightly drier soils than normal. With a forecast of more precipitation (significant in many places) over the next week, this could definitely curtail early planting where soils are warm enough to plant.
In contrast, much of the southern and eastern U.S. was dry with widespread SMI values of -3 and -4. This was reflected on the latest U.S. Drought Monitor with abnormal dryness and moderate drought occurring along the Gulf Coast and into South Carolina. Improvement was noted in much of South Carolina as received significant precipitation last week led to soils being considerably more moist than a week earlier.
Further north into the mid-Atlantic and northeast corridor, the SMI is indicative of somewhat drier than average conditions. This isn’t indicative of drought at this point, but it will be worth watching if precipitation later this week fails to materialize and these current anomalies persist for another few weeks.
Please direct any feedback or questions my way ( Eric.Hunt@aer.com ).